Okay Specs first

2004 Mazda 6 wagon. 112k miles 3.0L

Problem : In trying to start the car, : Engine chugs for a second (as if trying to run and start) but no bueno. repeated attempts to start has 0 chugging no start, engine turning over at normal speed. ..

Things we know and tested so far.: Removed front 3 plugs and tested compression. 160psi on all three (cold) Spark detected on all three plugs (bright blue/white), vaporized fuel being ejected from open plug holes (injectors working) Have not pulled throttlebody/manifold to test compression/spark on back half.

However with 3 plugs out, it turns over as if it has compression on the back half.

No codes thrown. none in memory. Battery replaced and is fully charged (probly because of the dead battery we have no codes.. car sat for 9 months untouched)

Previous owner described issue leading up to current condition.. "car ran fine, then at stoplight it stalled.. took a bit but restarted normally, drove home, stalled again, on restart it was doing what it is doing now" (current condition)

I should mention I am a mechanic, but not terribly familiar with the 6 series 3.0.

Suspect back half cam posi/angle sensor bad, no fire condition for those back half cyls timing error by compy keeping it from running. But no codes is throwing me.

Note, on some starts with key in "run" position , I hear a frantic buzzing near and about the throttle body. Is this normal?

Also , say this is put back into running condition .. what of any parts should be replaced at this time?

Thank you for your time. .